1. Technical Field
The present invention relates to an inflator, and particularly relates to an inflator for an inflatable vehicle occupant protection device, such as an air bag.
2. Description of the Prior Art
An inflator for an inflatable vehicle occupant protection device, such as an air bag, includes a source of inflation fluid. The source of inflation fluid may be an ignitable material which, when ignited, rapidly generates a large volume of inflation fluid in the form of gas. The inflator may alternatively contain a stored quantity of pressurized inflation fluid, or a combination of pressurized inflation fluid and ignitable material for heating the inflation fluid.
The inflator typically includes an initiator which is actuated electrically when the air bag is to be inflated. The initiator typically includes an ignitable or pyrotechnic material. Actuation of the initiator effects flow of inflation fluid from the inflator into the air bag to inflate the air bag.
Some inflators are of the "dual stage" type and include two independently actuatable initiators. The two initiators can be energized simultaneously, or at different times, to control the rate of flow of inflation fluid from the inflator. In some cases, only one of the initiators is energized, for example, when a relatively low fluid flow rate is desired. In these cases, any ignitable material in the second initiator remains active, that is, unignited. It is desirable, for safety reasons, to deactivate the ignitable material in the second initiator when the second initiator is not electrically energized.